Mont Blanc (UK: ; US: ) is a mountain in the Alps, rising 4,807.3 m (15,771.9 ft) above sea level, located right at the Franco-Italian border. It is the highest mountain in Europe outside the Caucasus Mountains, the second-most prominent mountain in Europe (after Mount Elbrus in Russia), and the 11th most prominent mountain in the world.
The mountain gives its name to its range, the Mont Blanc massif, which straddles parts of France, Italy, and Switzerland. Mont Blanc's summit lies on the watershed line between the valleys of Ferret and Veny in Italy, and the valleys of Montjoie, and Arve in France. Ownership of the summit area has long been disputed between France and Italy.
The Mont Blanc massif is popular for outdoor activities such as hiking, climbing, and trail running and winter sports such as skiing and snowboarding. The most popular climbing route to the summit of Mont Blanc is the Goûter Route, which typically takes two days.
The three towns and their communes which surround Mont Blanc are Courmayeur in Aosta Valley, Italy; and Saint-Gervais-les-Bains and Chamonix in Haute-Savoie, France. The latter town was the site of the first Winter Olympics. A cable car ascends and crosses the mountain range from Courmayeur to Chamonix through the Col du Géant. The 11.6 km (7+1⁄4 mi) Mont Blanc Tunnel, constructed between 1957 and 1965, runs beneath the mountain and is a major transalpine transport route.
Mont Blanc and adjacent mountains in the massif are predominantly formed from a large intrusion of granite (termed a batholith) which was forced up through a basement layer of gneiss and mica schists during the Variscan mountain-forming event of the late Palaeozoic period. The summit of Mont Blanc is located at the point of contact of these two rock types. To the southwest, the granite contact is of a more intrusive nature, whereas to the northeast it changes to being more tectonic. The granites are mostly very-coarse grained, ranging in type from microgranites to porphyroid granites.
The massif is tilted in a north-westerly direction and was cut by near-vertical recurrent faults lying in a north–south direction during the Variscan orogeny. Further faulting with shear zones subsequently occurred during the later Alpine orogeny. Repeated tectonic phases have caused breakup of the rock in multiple directions and in overlapping planes. Finally, past and current glaciation caused significant sculpting of the landscape into its present-day form.
The first systematic account of the minerals of the Mont Blanc area was published in 1873 by Venance Payot. His list, entitled "Statistique minéralogique des environs du Mt-Blanc", catalogued 90 mineral types although it also included those present only as very small components of rocks. If these are excluded, it is known today that at least 68 separate mineral species occur across the wider range of the Mont Blanc massif.
Located on the watershed between the Rhône and the Po, the massif of Mont Blanc is also situated between the two different climatic regions of the northern and western Alps and that of the southern Alps. Climatic conditions on the Mer de Glace are similar to those found on the northern side of the Swiss Alps.
The climate is cold and temperate (Köppen climate classification Cfb), and is greatly influenced by altitude. Being the highest part of the Alps, Mont Blanc and surrounding mountains can create their own weather patterns. Temperatures drop as the mountains gain in height, and the summit of Mont Blanc is a permanent ice cap, with temperatures around −20 °C (−4 °F). The summit is also prone to strong winds and sudden weather changes. Because of its great overall height, a considerable proportion is permanently glaciated or snow-covered and is exposed to extremely cold conditions.
There is, however, significant variation in precipitation with altitude. For example, the village of Chamonix below Mont Blanc is at an elevation of approximately 1,030 m (3,380 ft). It receives around 1,020 mm (40 in) of annual precipitation, whilst the Col du Midi, which is at 3,500 m (11,500 ft) above sea level, receives significantly more, totalling 3,100 mm (122 in). However, at an even higher altitude (near the summit of Mont Blanc), precipitation is considerably less, with only around 1,100 mm (43 in) recorded, despite the latter measurements being taken at the height of 4,300 m (14,100 ft).
The Mont Blanc was the highest mountain of the Frankish Empire under Charlemagne and the highest mountain of the Holy Roman Empire until 1792.
Pierre Martel's 1744 map and sketch of the Chamonix valley contains what is considered the first printed appearance of the name "Mont Blanc".
In 1760, Swiss naturalist Horace-Bénédict de Saussure began to go to Chamonix to observe Mont Blanc. He tried to summit it with the Courmayeur mountain guide Jean-Laurent Jordaney, a native of Pré-Saint-Didier, who accompanied De Saussure since 1774 on the Miage Glacier and Mont Crammont.
The first recorded ascent of Mont Blanc (at the time neither within Italy nor France) was on 8 August 1786 by Jacques Balmat and the doctor Michel-Gabriel Paccard. This climb, initiated by Horace-Bénédict de Saussure, who rewarded the successful ascent, traditionally marks the start of modern mountaineering. The first woman to reach the summit was Marie Paradis in 1808.
At the scale of the Mont Blanc massif, the border between Italy and France passes along most of the main Alpine watershed, from the Aiguille des Glaciers to Mont Dolent, where it reaches the border with Switzerland. However, its precise location near the summits of Mont Blanc and nearby Dôme du Goûter is disputed. Italian officials claim the border follows the watershed, splitting both summits between Italy and France. In contrast, French officials claim the border avoids the two summits, placing them entirely with France. The size of these two (distinct) disputed areas is approximately 65 hectares (160 acres) on Mont Blanc and ten hectares (25 acres) on Dôme du Goûter.
In 1723, the Duke of Savoy, Victor Amadeus II, acquired the Kingdom of Sardinia. The resulting state of Sardinia was to become preeminent in the Italian unification.
Citing the Treaty of Paris (1796), France claims that the historical border of Savoy and Piedmont diverged from the watershed line, fully encompassing the summit of Mont Blanc within Savoy and consequently, within French territory.
After the Napoleonic Wars, the Congress of Vienna restored the King of Sardinia in Savoy, Nice, and Piedmont, his traditional territories, overruling the 1796 Treaty of Paris. Forty-five years later, after the Second Italian War of Independence, it was replaced by a new legal act. This act was signed in Turin on 24 March 1860 by Napoleon III and Victor Emmanuel II of Savoy, and deals with the annexation of Savoy (following the French neutrality for the plebiscites held in Tuscany, Modena, Parma and Romagna to join the Kingdom of Sardinia, against the Pope's will). A demarcation agreement, signed on 7 March 1861, defined the new border. With the formation of Italy, for the first time, Mont Blanc was located on the border of France and Italy, along the old border between the department of Savoy and that of Piedmont, formerly belonging to the Savoyard state.